1. Field of the Invention
The invention relates to a transaxle with a brake, for use in a vehicle, such as a buggy or all-terrain vehicle, which can travel on ground in bad condition, such as uncultivated land, grassland, sandy soil, a riverbed or pressed snow, regardless of such a bad ground condition. The invention especially relates to a device for cooling the brake of the transaxle.
2. Related Art
A vehicle, such as a buggy or all-terrain vehicle, travels by high-speed rotation of an axle receiving a high-speed input rotation. The vehicle is provided with a brake disposed around an input shaft for inputting the rotation force to the axle, and a rotatable friction member of the brake is relatively unrotatably fitted on the input shaft so as to be rotated integrally with the input shaft. During travel of the vehicle, the rotatable friction member rotates at high speed and agitates lube below it, and the lube resists the agitation so as to be heated. Additionally, an unrotatable friction member is relatively unrotatably fitted to an unrotatable portion such as a transaxle housing so as to be rotatable relative to the rotatable friction member and the input shaft, and during activation of the brake, the rotatable friction member is frictionally pressed against the unrotatable friction member so as to cause heat. Therefore, the vehicle requires a structure for efficiently cooling the brake.
Conventionally, as disclosed in Japanese Patent No. 3,052,075, there is a well-known lube circulation system comprising upper and lower lube passages interposed between a brake housing incorporating the brake and a reduction casing incorporating a reduction drive train. A rotating rotary component, e.g., a gear, of the reduction drive train agitates a lube sump in the reduction casing and splashes lube from the lube sump. A part of the splashed lube flows through the upper lube passage and enters an upper portion of the brake housing so as to cool the brake therein, and then, falls into a lower portion of the brake housing and returns to the lube sump in the reduction casing through the lower lube passage.
However, since the majority of lube splashed from the lube sump is hit against an inside wall surface of the reduction casing by a great centrifugal force and falls to return to the lube sump, the quantity of lube entering the brake housing through the upper lube passage is so small as to reduce the efficiency of cooling the brake.
To sufficiently cool the brake, the rotary component of the reduction drive train is required to be more deeply submerged into the lube sump so as to increase the splashed lube. However, the increase of depth of the rotary member submerged in the lube sump means rising of the lube level in the brake housing, so that, during traveling of the vehicle, the resistance of lube against the agitation by the rotating member of the brake is increased so as to increase power loss and heat.
An additional problem is large deviation of the brake cooling effect during travel of the vehicle on a rough land because the traveling vehicle is tilted so as to prevent evenness of the depth of the rotary component submerged in the lube sump.